Clever: Smart::Transient:

The word that best completes the analogy Clever:Smart::Transient: is Temporary.

• Clever means having or showing quick and sharp intelligence or wit.
• Smart means having or showing intelligence or mental ability.
• Transient means lasting for a short time only.
• Temporary means lasting for a short time only.
• Translucent means allowing light to pass through so that objects behind can be seen indistinctly.
• Changeable means liable to change or be changed.
• Doubtful means not certain or reliable.